As the wireless communication business continues to grow, there are great demands in further cost reduction, and to use semiconductor manufacturing processes and component techniques that can handle very high-volumes during the short product cycles of many of the new devices. The ever-increasing market for microwave power amplifiers in PCS, CDMA and WCDMA systems requires low-cost ease-of-use technology, which can provide high-power and good linearity performance.
LDMOS started replacing bipolar devices in base station applications 3–4 years ago and has for multiple reasons become the leading technology for base station power amplifier applications. It has high gain and shows excellent back-off linearity. For the output power amplifier however, discrete devices are still dominating.
Integrated power amplifiers in LDMOS silicon technology, moderately integrated as MMIC's (microwave monolithic integrated circuits), have only recently found its way from the research and development laboratories, see e.g. G. Bouisse, “Latest Advances in High Power Si MMIC”, IEEE Eumw, GaAs symposium 2001, and G. Bouisse, “0.2 db gain ripple-20W-WCDMA Si MMIC”, IEEE EuMC-ECWT symposium 2001.
The integration of LDMOS transistors into RF BiCMOS processes without affecting other devices is described in the published U.S. patent application No. 20020055220 A1, and in O. Bengtsson, A. Litwin, and J. Olsson: “Small-Signal and Power Evaluation of Novel BiCMOS-Compatible Short Channel LDMOS Technology”, IEEE Transactions on Microwave Theory and Techniques, Vo. 51, No. 3, March 2003. This opens a way to low cost and more efficient linear integrated radio frequency power amplifiers with multiple amplification steps on the very same die.